The GA-100 Global Amplifier provides universal compatibility to virtually every telephone requiring the use of a modular amplifier. With its simple connection to the handset port of your phone and fine-tune transmit and receive volume adjustments you will achieve unmatched sound quality and clarity on every single phone call. The exclusive Multi-Purpose Utility Port tm allows two people to connect seamlessly to the same call for supervising or training purposes. Choose any standard series headset mode Additional Details ------------------------------ Product description: The GA-100 Global Amplifier provides universal compatibility to virtually every telephone requiring the use of a modular amplifier. With its simple connection to the handset port of your phone and fine-tune transmit and receive volume adjustments you will achieve unmatched sound quality and clarity on every single phone call. The exclusive Multi-Purpose Utility Port tm allows two people to connect seamlessly to the same call for supervising or training purposes. Choose any standard series headset mode